Realizing Ultrahigh Mechanical Flexibility and >15% Efficiency of Flexible Organic Solar Cells via a “Welding” Flexible Transparent Electrode

Abstract

The power conversion efficiencies (PCEs) of flexible organic solar cells (OSCs) still lag behind those of rigid devices and their mechanical stability is unable to meet the needs of flexible electronics at present due to the lack of a high‐performance flexible transparent electrode (FTE). Here, a so‐called “welding” concept is proposed to design an FTE with tight binding of the upper electrode and the underlying substrate. The upper electrode consisting of solution‐processed Al‐doped ZnO (AZO) and silver nanowire (AgNW) network is well welded by utilizing the capillary force effect and secondary growth of AZO, leading to a reduction of the AgNWs junction site resistance. Meanwhile, the poly(ethylene terephthalate) is modified by embedding the AgNWs, which are then used to link with the AgNWs in the upper hybrid electrode, thus enhancing the adhesion of the electrode to the substrate. By this welding strategy, critical bottleneck issues relating to the FTEs in terms of optoelectronic and mechanical properties are comprehensively addressed. The single‐junction flexible OSCs based on this welded FTE show a high performance, achieving a record high PCE of 15.21%. In addition, the PCEs of the flexible OSCs are less influenced by the device area and display robust bending durability even under extreme test conditions.

Benefits, Problems, and Solutions of Silver Nanowire Transparent Conductive Electrodes in Indium Tin Oxide (ITO)‐Free Flexible Solar Cells

“…[172] Although AgNWs are mostly used as anodes in conventional and inverted (with reverse geometry) OSCs to replace ITO electrodes, many investigations have focused on inverted organic solar cells (IOSCs) using AgNWs as cathodes. [140,151,230,[256][257][258][259] In fact, in comparison with conventional OSCs (COSCs), IOSCs showed improved air stability and a higher device lifetime. The structures of the OSCs and IOSCs are shown in Figure 24.…”

“…devices based on Em-Ag/AgNWs-SG and PET/ITO electrodes retained 60% and 61% of their initial PCEs after 6 days of exposure, respectively (below that of ITO glass), due to the poor oxygen-barrier abilities of the PET substrate. [257] It is worth mentioning that, currently, the highest PCEs of rigid single-junction OSCs have reached up to 17.3%; [258] however, the equivalent of flexible OSCs is merely 15.21%. [257] The reason for the inferior performance of the flexible OSCs devices based on AgNWs@PI and on PI/AgNW (the inset) electrodes.…”

“…[257] It is worth mentioning that, currently, the highest PCEs of rigid single-junction OSCs have reached up to 17.3%; [258] however, the equivalent of flexible OSCs is merely 15.21%. [257] The reason for the inferior performance of the flexible OSCs devices based on AgNWs@PI and on PI/AgNW (the inset) electrodes. AgNWs@PI denotes AgNWs embedded in the PI substrates.…”

Novel Bimodal Silver Nanowire Network as Top Electrodes for Reproducible and High‐Efficiency Semitransparent Organic Photovoltaics

“…[ 23 ] Although AgNWs demonstrate many outstanding properties, to date, considerable efforts have mostly been devoted to the incorporation as transparent bottom electrodes to replace indium tin oxide (ITO) for highly efficient OPVs with reflective top electrode. [ 24–29 ] It was found that postprocessing treatments, such as high‐temperature thermal annealing (200 °C for 10–30 min), mechanical pressing, and so on, are usually required to reduce the contact resistance between the nanowires and hence achieve a desired electrical conductivity. Obviously, these treatments limit AgNWs in applications where it is used as the top electrode, especially for the devices that contain heat‐sensitive semiconducting materials, where postprocessing temperature can critically and negatively impact a carefully created and optimized morphology.…”

A Terpolymer Acceptor Enabling All‐Polymer Solar Cells with a Broad Donor:Acceptor Composition Tolerance and Enhanced Stability

“…[20,21] These combined merits indicate that all-PSCs hold a great potential for large-area manufacturing of flexible optoelectronics using printing-based techniques. [22,23] BHJ film morphology with nanoscale phase separation and bicontinuous interpenetrating network is one of keys for achieving highly efficient OSCs. [24][25][26][27][28][29][30] Among various morphology tuning strategies, varying the donor:acceptor (D:A) ratio in BHJ active layer plays a primary and critical role.…”